Leases Maturities of lease liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2020	$ 35
2021	27
2022	23
2023	21
2024	18
Later years	132
Total lease payments	256
Less amounts representing interest	(46)
Total lease obligations	210
Finance Lease, Liability, Payment, Due [Abstract]
2020	42
2021	40
2022	31
2023	23
2024	18
Later years	70
Total lease payments	224
Less amounts representing interest	(80)
Total lease obligations	$ 144	$ 167